1. Field of the Invention
This invention relates to a head slider which moves over a storage medium in an external storage device such as a magnetic disk drive or an optical disk drive. More particularly, this invention relates to a floating head slider having air bearing surfaces which are separated from the disk surface when the head is stationary, yet do not accumulate excessive dust, and can be cleaned in areas of the disk surface provided for cleaning purposes.
2. Description of the Related Art
In disk drives, a CSS (Contact Start and Stop) system is generally adopted for head sliders which float over a storage medium such as a disk in such disk drives. In the CSS system, the head slider is positioned at a CSS zone on part of the surface of the disk medium when the disk drive is stationary. When the disk medium rotates, the head slider floats (or flies) over the surface of the disk medium of the disk drive.
A head slider is generally equipped with reading and/or writing heads. Recent magneto-optical disk drives are also equipped with a magnetic head for application of magnetic fields on the disk in reading and/or writing. Furthermore, on a test basis, an optical head including an optical element such as an object lens or a light emitting element has been installed on a head slider in order to allow a source of light to impinge onto a disk medium.
Such a slider is supported by a suspension, and is moved over the surface of a disk medium by maneuvering the suspension radially across the disk. The head slider floats due to the effect of the air flow over the surface of the rotating disk medium, or a principle of an air bearing force created by the dynamic pressure mechanism on the surface of disk medium.
In recent disk drives, there has been a trend toward lowering the floating height of the floating head slider to accommodate the faster pace with which advances are being achieved in high storage densities, as well as miniaturization. However, lowering the floating height may lead to other problems. For example, reducing the floating height of the slider may increase the risk that the slider will come into contact with projections on the disk surface, causing damage to the contacting surfaces. Consequently, efforts have been made to reduce the roughness of the disk surface to prevent the disk from coming into contact with the head when the floating height of the slider is lowered. However, the less disk surface roughness there is, the greater the contact area of the CSS zone and the more easily the slider will stick to the disk through adsorption. If the adsorption force is large enough, the disk driving motor will bear a heavier load and the suspension supporting the head may be damaged.
To reduce the adsorption force, some ideas have been disclosed, e.g., Japanese Laid open patents Tokkai-sho 63-37874 and Tokkai-hei 8-212740, in which a pad (also referred to as a projection) is attached to the air bearing surface (also referred to as a floating surface or rail surface) of a head slider facing a disk surface, to reduce the contact areas between the slider and the disk medium.
FIGS. 1(a) and 1(b) show head sliders based on the previous technology, depicting the surface which faces the disk medium (floating surface) and the air inflow end, respectively. Slider rails 92 and 93, and pads 94a, 94b, 94c and 94d attached to rail surfaces 92b and 93b are installed onto the surface facing the disk on head slider 90.
FIGS. 1(c) and 1(d) depict the surface of the side and the surface facing the disk (floating surface), and present some problems with the prior technology. Since the pads 94a, 94b, 94c and 94d project from the rail surfaces, which are the air bearing surfaces, airborne dust G inside the disk system tends to accumulate in the peripheries of pads 94a, 94b, 94c and 94d, conveyed by the air flow R created by rotation of the medium. As the amount of accumulated dust increases, fluctuations in the floating condition may eventually develop, resulting in system problems such as faulty recording/playing responses and head failures. Thus, there is a need for such head sliders which do not accumulate dust in this manner. There is also a need for disk arrangements by which the rail surfaces can be cleaned in service.